AR buffer tube problem

[Shadow9mm]

Working on my supervisors rifle, He bought the upper from another co-worker already built.

There were a number of issues, but the one I am fighting right now is the buffer tube. The tube sounds funny. Kind of like a noisy zipper, or a zip tie.

I swapped in a buffer and spring from my rifle which helped a lot, but did not entirely fix the problem

I swapped his spring back in, no difference.

So at this point I am thinking its 80% the buffer and 20% the tube itself.

Which brings me to my next issue. The buffer tube seems to be some sort of enhanced or extended tube. it has tines and a slot in the bottom for the buffer detent to go into.

From appearances the buffer tube was not screwed in all the way. so I screwed in in the rest of the way. However now the stock wont lock into the first detent.... SMH... this poor gun needs some TLC.

So at this point I am not sure what to recommend. I'm honestly leaning towards suggesting he replace the buffer and buffer tube as he really seems to want to get rid of the sound. But again, I's making my best guess as to what is causing it based off some process of elimination testing. I can guarantee it will fix it.

I apologize in advance, the pics I took are not good.

As I got it, not screwed in enough?




After I screwed it in the rest of the way.

[44 AMP]

However now the stock wont lock into the first detent...

I believe this should be your clue. (but, not about the noise..)

Mind you, this is just a guess, but you're using one of the collapsible stocks, and the buffer tube is held in position with a nut/flange, of some kind??

The notch in the buffer tube where the detent locks in is from the original AR/M16 (fixed stock) design, where there is nothing else to prevent the tube from unscrewing. If you're using the collapsible stock system where the tube in held in place a different way, then there is no need to have the tube screwed in so the buffer detent locks into the notch, and I believe that is what you have, the tube screwed in only to the point the stock will lock into its detents.

As to the funny noise, I have no clue. It doesn't affect function in any way, does it??

[Shadow9mm]

yes, the castle nut is holding the tube onto the receiver. The stock is hitting bottoming out on the castle nut. I'm just confused, it does not seem right either way. its either not screwed in enough, or its screwed in too far.

Yes, using a collapsable stock. It seems to be some kind of proprietary "enhanced" buffer tube similar to the Aero enhanced tubes. with the slot for the buffer detent. I am just worried screwing it back out 1 full rotation to its previous position, it is not securerly/properly causing the detent. and having the detent come loose would cause a far bigger problem than having the stock not lock into the shortest position.

as far as the noise goes, my boss really does not like it. its kind of between metal scraping and a zipper. most of the noise went away when i swapped out the buffer from my rifle. but it is loud, and metal scraping is never a good sound, and generally does not bode well.

[44 AMP]

Just to be clear, this is a privately owned gun, not something issued by some agency, right???

Because if it is, I'd say turn it in for repair and draw another one.

But if its his personal gun, then its all on him (and you I suppose).

What APPEARS to be the issue is a mismatch between who ever made the tube and the who ever made the lower receiver's specs.

OR it might be the stock assy. Including the castle nut.

In the first picture, where the tube is "screwed out" enough so the stock locks into its forward detent, the buffer tube is BARELY retaining the buffer detent. Literally, only a tiny corner of the tube at the edge of the notch is holding in the detent.

This is NOT right, and not very secure and I would expect it to break at any time with no warning. The tube should be screwed in the way you show it in the second picture.

My guess would be that the receiver comes from one maker, the tube from another and possibly the stock from yet another and the set up is a victim of stacking tolerances. Possibly what was done was that the rifle was assembled properly, but the stock wouldn't latch in, so the builder turned the tube out, until it did, and since it still retained the buffer detent, called it good and sent it out to the consumer that way.

Couple of questions, have you inspected the tube, inside and out for any dent, or burr inside? Even a small one would sound like a stick on a picket fence when the spring rubs over it.

Other question, when the stock does latch into its forward position, it is hard up against the castle nut? Is it possible the reason it won't latch into proper place when the tube is screwed in correctly because the nut is too thick to allow that??

If you have the parts to swap and check with, pull the tube (and stock) off a rifle that IS properly set up (tube fully screwed in to retain the buffer detent, and put it on the boss's rifle. See if the stock from the boss's rifle works on the "new" tube. OR if only the stock that was with the new tube on the other rifle works. Also compare the nuts on the bosses rifle and the one you're "borrowing" parts from.

Somewhere there is a difference in specs. I don't see any other possibility.
Good luck and do let us know what you find out.

[stagpanther]

When I look at your pictures--which are a bit out of focus so I can't tell for sure--what jumps out at me is the impact points on both the lower's ears as well as the end of the buffer tube itself. Even the detente pin looks a bit deformed from hits.

This is almost always the result of a mismatch between the buffer length, buffer tube length and bolt carrier. If that's the case, your rifle is beating itself and you up. Just an edge of the buffer tube holding the retaining pin is nothing to get excited about, that's how most of them work.

A "quick and dirty" check is to remove the assembled lower from the upper--then take the BCG out of the upper and use it to push back on the buffer in the lower (make sure it's properly aligned). The buffer should stop the back of the carrier just shy--like maybe a thousandths or two inches--from contacting the lower's ears (or anything else--it almost looks like the buffer tube itself is taking hits to me).

addendum--a closer look and the alignment of you buffer tube and it looks "out of clock" with the buffer retention pin judging by the deformation(s).

[Shadow9mm]

Its his personal weapon. Otherwise i wouldn't be messing with it, our Armour/smith would be.

The upper and lower are a snug fit.

I got it back to him this morning, as he is wanting to shoot it this weekend. Ill do some more poking around next time i have it.

I did reccomended a new buffer and tube, he gave me the go ahead, got him botn Aero precision parts. Told him if it does not fix the problems i will deal with the return.

The gun is sketchy, i suspect its a leftover parts build. The hand guard is a Hera, but has a bend in it from someone yanking on a vertical grip too hard. The hand guard is wiggly. Its missing 2 of its clamping screws. Im waiting to hear back from Hera on replacements. The gas key is not properly staked. Noted buffer tube problems. Trigger is 8lb. Muzzle brake was installed upside down. Big 3 port brake woth some vent holes on one side. The vent hokes were facing down, pushing the muzzle up.... bolt and carrier had red wheel bearing grease on them. Last outing, first time he shot it he had 3 failures to fire out of 20. Were hoping it was the grease/dirt. I cleaned and properly oiled it.

but it passed my go/no-go gauges so its safe enough. Bolt is narked mpi. Hes gonna shoot this weekend, hopefully no more failures to fire and we can work in it from there.

[stagpanther]

My money is still on length mismatch between tube, buffer and carrier. Fortunately, AR parts remain very cheap, your friend might find it's simply easier to start from scratch rather than "rescue" a frankenbuild with multiple hardships.

[Shadow9mm]

Ill take some measurements when im changing out the buffer and tube, see what its looking like. My money is on an out of spec tube at the moment.

[101combatvet]

I converted a rifle to a carbine with folding stock. I purchased the folding stock with all the parts and just slapped it on. It works flawlessly. It sounds like whoever built your rifle used a mismatch of components.

[Shadow9mm]

Its a franken gun for for sure. But he seems pretty happy with it, other than the buffer tube noise. Trying to fix what he wants fixed, and what needs fixed.

[FrankenMauser]

If the 'twoing' and manual cycling noise are the only real issues, he probably won't be happy until a Silent Capture assembly is stuffed in there.

[ocharry]

well , i think if it were mine i would see if the guy he got it from would give a refund and look for another rifle....probably not gona happen that way but worth a ask

and if that didnt work out me thinks my next move would be to take it apart and see what was messed up in the build to start with and fix it all at once

using the stuff that is OK and replacing the stuff that is not

yeah not the cheapest way to do it but at least you know what you have

i have 3 of those forked buffer tubes, mine are aero and they say that is to help with bolt tilt...the back end of the bolt should rest while in battery on the forks and they help guide the bolt into the tube

the first one i got was for a piston gun i have..ruger sr556, i changed the original before i ever shot it..i also changed the spring and buffer to the buffer and spring from heavybuffers.com this guy has it dialed in

anyway the three i have are quiet and no noise, all are from aero with thier spring and buffer except the sr556 and it has the anti tilt spring and buffer from heavy buffers

so you should check the inside of the buffer tube to see how ruff it is....something has to be raking that spring in recoil

just a thought and my .02

ocharry

[Shadow9mm]

not sure if its raking the spring, or the buffer. looked down the tube itself, looked ok, Wondering if its the metal itself before it was finished, or the way in which the finish itself was applied. I looked at the pics, its forked, but pretty sure its not an aero. And I am pretty sure the tube is out of spec. He did give me the OK to order a new buffer and tube. hopefully that fixes the problem. If not I will return the parts and give him his parts $ back.

[ocharry]

i guess if push comes to shove the lower could be out of speck..manufacturer could have missed the location on that hole...what lower is it?? could be a bad tube ......could just be tolorance stacking like has been said

also my aero parts went into the reciever and captured the detent like your secound pic and the stocks go to the short hole just fine, so to get the stock to go into the closest hole for the short set up maybe the castle nut is to thick or the nose of the stock is to long....so ..how far does the stock pin miss the hole in the close tube hole...half a hole, just a few thousands??? could you shave the nose on the stock to get there or maybe the back of the castle nut, or get a different castle nut that is thinner?? that too is just a thought

i for one would really like to see what you find and what solution you were able to come up with

i still say take it apart and start from scratch...lol

ocharry

ocharry

[44 AMP]

This kind of thing is the problem we run into with "everybody and their Uncle Max" making ARs (and 1911A1) and their parts.

Often different makers will "tweak" something just enough so it works with the other parts that THEY make, but not so well with parts made by other makers.

My son has a S&W 1911 pattern gun. Great gun, well made, accurate, etc. Will take GI magazines. Will NOT take GI (standard Colt) pattern grips. The grip screw bushings are spaced just a tiny bit too far apart to fit the holes in standard grips. S&W grips fit perfectly.

Seems like, these days, the only way to be relatively certain that all your parts will fit together properly (not just well enough to work, but correctly) is to get them all from the same maker. Otherwise, you're rolling the dice, and once in a while, you will crap out.

Good Luck with the fix and let us know how it goes!

[Shadow9mm]

Originally Posted by ocharry

i guess if push comes to shove the lower could be out of speck..manufacturer could have missed the location on that hole...what lower is it?? could be a bad tube ......could just be tolorance stacking like has been said

also my aero parts went into the reciever and captured the detent like your secound pic and the stocks go to the short hole just fine, so to get the stock to go into the closest hole for the short set up maybe the castle nut is to thick or the nose of the stock is to long....so ..how far does the stock pin miss the hole in the close tube hole...half a hole, just a few thousands??? could you shave the nose on the stock to get there or maybe the back of the castle nut, or get a different castle nut that is thinner?? that too is just a thought

i for one would really like to see what you find and what solution you were able to come up with

i still say take it apart and start from scratch...lol

ocharry

ocharry

I agree with you, If I could gut it and start over I would. But its not my gun or my money. I did what I could, pointed some things out, fixed what I could, gave him my recommendations. He did what he felt like doing, buffer and tube to get rid of the noise was all he wanted to do.

Anderson lower if I remember correctly. I will check the spec on the hole placement when I get it back to put the new buffer tube on.

[stagpanther]

Did you check the length of the buffer, buffer tube and whether or not the carrier is bottoming out on either the lower's ears or tube end? That's what I see in the pictures you posted. The difference in the two pictures is several turns in the buffer tube and covers quite a bit of distance. The first picture looks like the castle nut lock on the buffer tube had gone loose and the tube rotated--though it's hard to imagine it making complete rotations without the owner knowing it.

Just curious--what do you mean by the gas key is not properly staked? (pic?)

[HiBC]

I think you got it right in the pic labeled "Fixed" regarding the buffer screwed in to correct depth.
While the buffer retainer does index into a notch ,the notch mechanically retains the plunger so it does not get lost.
Yes,it indexes the tube for assembly, but thats not the strength of the assembly. Torque the tube against the buffer retainer and you do damage. The key in the plate ,the keyway in the tube,the dimple and the castle nut provide the strength

It sounds like the "stock won't latch" problem could be from the vast and variable buttstocks. I'd trust Magpul, Rock River, Aero,etc name brand buttstocks.
Plates vary some with sling attachment designs, Castle nuts can be "Different" as in extra length. I'd get my eyeball on it and identify where the interference is.It might need a mil spec castle nut or a couple of file strokes on the buttstock. I cant tell you without looking at it.

The noise? AR's are known to make a spring noise. I take it this is an unusual noise. Check the wire ends of the springs for burrs or deformaties.
Spring to buffer friction can make a little noise. A light (almost none!) film of grease on the outside of the buffer might help. Don't gunk it up (Cold sluggish and dirt magnet)

Venting...There is an air compression thing during cycling. I guess it could find a way to make noise

You said the gas key is not staked right. If that affects BCG clocking the BCG might chew on the buffer retainer.

One more place to look. Does it have a forward assist? Of its found a way to drag on the BCG it would make noise.
The pic that says "Screwed all the way"shows some "ding" on the buffer tube and wear on the tip of the buffer retainer. I'd figure those out.

Being a free gunsmith under pressure is fun,huh?

I say "I don't have an ffl. I don't take on work. Take it to Acme Tacticool"

[Shadow9mm]

So i replaced the buffer tube today. The one on the gun was probably 1/8 of an inch shorter than the new mil-spec one. After installing the odd scraping noise is gone. And the stock will now fully collapse and lock in to the first detent. And i installed the remaining handguard screws and its rock solid. Boss is happy, and im glad its done.

[stagpanther]

Sounds like the twilight zone of parts--but you got it running again and that's the important thing.

[Shadow9mm]

Originally Posted by stagpanther

Sounds like the twilight zone of parts--but you got it running again and that's the important thing.

Not a bad way to put it.